Senate races can have coattails for gubernatorial contests, but the impact is far from guaranteed.

As we head into the busiest year of the four-year gubernatorial cycle -- and into the six-year-itch election that usually hammers the party of a second-term president -- it's reasonable to ask whether the Democrats' potentially dicey electoral chances in the Senate could impact November's gubernatorial races.

To get a handle on this question, we looked at the interplay between Senate and gubernatorial races in 2006 and 2010, as well as the current state of play for such races in 2014. We found that Senate contests can have negative coattails for a gubernatorial race, but also that the severity of the impact on a party's fortunes depends on how many states have dual competitive races in a given election cycle.

In 2014, as it turns out, there simply isn't much overlap between the states holding gubernatorial and Senate contests. In fact, just three states have both a competitive gubernatorial race and a competitive Senate race right now:

Colorado, where Democratic Sen. Mark Udall is facing a strong challenge from GOP Rep. Cory Gardner, and where Democratic Gov. John Hickenlooper may face a tough re-election campaign;

And Michigan, where GOP Gov. Rick Snyder is facing a competitive re-election bid and where the retirement of Democratic Sen. Carl Levin has left a wide-open race.

There are three additional states that have at least one competitive race and a contest that is not currently competitive but which could become so -- Georgia, Minnesota and New Hampshire.

So how does 2014 compare to 2010? Four years ago, there were many more states with a pair of competitive statewide races -- seven, rather than three this year. Having more paired seats at risk obviously creates a bigger problem for the party facing headwinds that year, which in 2010, like this year, was the Democrats.

The states with two competitive contests in 2010 were California, Connecticut, Florida, Illinois, New Hampshire, Ohio and Wisconsin. Two other states -- Nevada and Pennsylvania -- had one competitive contest and another that was just slightly outside the competitive range. In a clear majority of the seven states, the same party won both seats. In just two states (Illinois and New Hampshire) did the voters split their tickets.

A state's general ideological leaning does make a difference. For instance, in a strongly Republican year, Democrats were able to prevail in both gubernatorial and Senate races in two solidly blue states -- California and Connecticut.

In Connecticut, "there was definitely a positive effect on organizing, from a field perspective," recalls Roy Occhiogrosso, a Democratic strategist in the state. And in California, the two Democratic campaigns -- that of gubernatorial candidate Jerry Brown and U.S. Sen. Barbara Boxer -- were "mutually reinforcing," sat Democratic strategist Garry South.

But in more marginal territory, like the purple states of Florida, Ohio and Wisconsin, the GOP wave of 2010 was enough to put Republicans over the top in both contests.

In Ohio -- where Republicans John Kasich and Rob Portman won the governorship and Senate seat, respectively -- "the Portman team was very strong and had deep organization, which helped the turnout," says Mark Weaver, a GOP strategist in the state.

And in Florida, the GOP in 2010 "regained their traditional advantage in mobilizing their supporters," says University of Central Florida political scientist Aubrey Jewett. "Without Obama at the top of the ticket and his organization, Democrats did not turn out in great numbers."

Not surprisingly, 2006 was more like the state of play now. Eight years ago, there was only a small overlap in competitive races. Just Maryland and Rhode Island had a pair of contests that fit the bill.

Of course, there's still time for states to drop off our dual-competitive list. In the Colorado gubernatorial race, for instance, the choice of a Republican nominee will have a sizable impact on how competitive the race ends up being. Several political observers in the state said that Hickenlooper's chances will rise if the GOP chooses a weak nominee -- even in the event that Udall stumbles.

"If the Republican nominee for governor is terribly flawed, voters could take their frustration out on Democratic legislators" rather than the governor, says GOP strategist Katy Atkinson.

Meanwhile, in Arkansas, the key question is how well the Democrats can insulate the gubernatorial race from national currents. "The Republicans are relying on anti-national Democrat and anti-Obama sentiments, while the Democrats are hoping that more positive candidate appeal will carry them forward," says Hal Bass, a political scientist at Ouachita Baptist University.

A recent poll suggests that the Senate seat may actually be in better shape for Democrats than the gubernatorial seat. According to an April New York Times-Kaiser Family Foundation poll, Pryor is 10 points ahead of Cotton, while in the gubernatorial race, former GOP Rep. Asa Hutchinson and former Democratic Rep. Mike Ross are in a dead heat.

However it plays out, the map of competitive races does at least give Democrats a measure of comfort. If a Senate meltdown materializes, Democratic gubernatorial hopes might be tweaked, but not dashed.